Heretofore, many paper diapers have utilized fluff pulp for absorbing the fluid. FIG. 7 of the accompanying drawings illustrates a typical structure of a paper diaper of the prior art. In the diaper of FIG. 7, a fluff pulp layer "b" of a certain thickness is disposed on a suitable support paper "a", a vinyl sheet "c" covers underneath the support paper "a", and a non-woven sheet "d" is placed on top of the fluff pulp layer "b". Side edges "e" and "e'" of the diaper are heat sealed, and both ends in the longitudinal direction, that is the direction perpendicular to the sheet of the drawing, are also heat sealed to provide a finished product. As to specific shapes of the product, there are flat ones for the adult, folded ones to fit the groin to be fastened about the waist, or rolled up ones with side edges shrunk for infants.
The fluff pulp which is used as a principal material of such paper diapers is produced relatively at a low cost and is well accepted by the industry. However, it is a mass of short fibers with the fibers being little entwined with each other, so that it is unable to maintain a given shape and collapses easily. Since the fibers are not entwined in the fluff pulp, and there exists substantial gaps or clearance between the fibers, there is generated no capillary action and the fluid cannot be transferred throughout the mass of fluff pulp. Despite these shortcomings, fluff pulp is generally used as the principal element of a liquid or fluid absorbing diaper.
Applicant has observed closely the conditions of absorbing and retaining the excretion, particularly fluid such as urine, and referred to generally herein as the fluid, and realized there are several problems that must be settled. The discharged fluid passes through the external member, that is the non-woven fabric "d", which is in direct contact with a human body, to permeate and sink into the fluff pulp layer "b", but such permeation and sinking of the fluid is substantially confined or limited to a local area R enclosed by dotted lines in FIG. 7. This area R is coextensive with an area of the diaper where the fluid excreted from the human body makes contact with the diaper. Even if the fluid permeates and sinks into the thickness of the fluff pulp layer "b", there is no spreading of the fluid in the lateral direction "x" of the diaper. Likewise, there is no spreading of the fluid in the longitudinal direction. The fluid merely sinks down in substantially perpendicular direction "z" causing the fluff pulp to cave-in. When a large quantity of fluid is discharged locally, the area R cannot retain the fluid within itself, and part of the fluid penetrates to the surface of the vinyl sheet "c" at the bottom and starts flowing out therefrom over in internal surface of the vinyl sheet "c". Some portion of the fluid seeps along the fluff pulp surrounding, and in contact with, the vinyl sheet, but since the fluff pulp is unable to absorb the fluid by itself, the amount of the fluid that so seeps is limited; most of this fluid collects on the vinyl sheet surrounding the area R and leaks laterally towards the side edges. In order to prevent this lateral leaking, it will become necessary to perform additional steps, for example, to tighten that part of the diaper which contacts the groin into a cup-like shape, or to shrink the side edges. Such will merely increase the manufacturing cost while serving little purpose of dispersing or diffusing the fluid. Further, if the lateral leakage is prevented by means of the additional steps just described, the area R becomes a gorge of the diaper when worn by a person. The fluid collects in this gorge-like part in quantity and wets the area R drippingly while the fluff pulp outside the area R is not wet at all. This condition is felt by a wearer who feels discomfort in using the diaper. Thus, the fluff pulp, which has been prepared for the purpose of absorbing and retaining the fluid, actually causes this localized "fluid collection" which brings about a contrary effect of giving the wearer a thoroughly wet feeling. In addition, most of the remaining fluff pulp does not function to absorb and retain the fluid, which means a gross waste or uneconomical use of a significant amount of the material making up the diaper.
In order to try and improve the poor performance in absorbing and retaining the fluid when using fluff pulp, it has been proposed to use high polymer absorbing material together therewith. Referring to FIG. 7, the high polymer absorbent can be inserted between the support sheet "a" and the fluff pulp layer "b". Pulverized polymer contained in the high polymer absorbent has a high degree of hydrophilic property and is capable of absorbing an amount of fluid sixty times its own weight, having the characteristics of taking in the fluid while it swells and is gelled. However, since it does not possess the property of dispersing fluid, it cannot transfer the fluid laterally to the remaining dry polymer, even when the polymer under the area R is saturated with the fluid. It is not only incapable of solving the problem of local "fluid collection" in the fluff pulp, but also presents another problem of increasing the product cost since the high polymer absorbent is expensive.